(1) Field of the Invention
The present invention relates to an error measuring method of gear, particularly for one can be used in association with a single gear flank tester.
(2) Description of the Prior Art
Currently, conventional gear measuring instrument popularly used in the industry is a kind of gear tester with a probing feeler of miniature ball in touching the flank of the gear tooth for determining the precision of the gear. However, such conventional gear measuring method can only be used for single gear with limitation for specific position on tooth profile, which is not suitable for determining related transmission error for a pair of mating gears (or called gear pair).
Therefore, for gears of high precision and low noise, a conventional single flank gear tester is often used to determining the precision and meshing condition of the gear pair. Normally, the conventional single flank gear tester mainly comprises a pair of mating and meshing gears (or called gear pair) containing an active gear (or called driving gear) and a passive gear (or called driven gear) with specific gear ratio and speed ratio thereof for effectively and smoothly transmitting torque and power of the active gear to the passive gear in accordance with the gear ratio and speed ratio thereof so that an expected output rotational speed and torque can be obtained functionally. However, in practically, certain intermittence may happen in the meshing action of the mating gear pair incurred by assembly error and process error. Usually, the intermittence is defined as transmission error of the gear pair. Additionally, with such conventional single flank gear tester, via analyses of profile error of each gear, accumulated pitch error of gears and adjacent pitch error of gears, the integrated transmission error of mating gear pair can be quickly determined so that it is suitably used for quality control (QC) in the industry.
For analysis the signals generated by the conventional single flank gear tester, the Fast Fourier Transform (FFT) is usually used with meshing frequency to divide the signals into high frequency and low frequency portions. Wherein, the high frequency portion, which mainly relates to tooth profile of the gear, is used to determine profile error of gear while the low frequency portion, which mainly relates to deflection of pitch circle in the gear, is used to determine accumulated pitch error of gears. Moreover, the relationship between the frequency and amplitude as well as the related features in the gear precision and transmission noise can be obtained by means of analysis in frequency spectrum for the signals.
The drawback for the Fast Fourier Transform (FFT) aforesaid is that it is difficult to define the meshing condition for the measured gear pair because certain phase shift or phase deviation is incurred by the filtering of wave frequency so that erroneous judgment on the gear precision is almost inevitable. Therefore, how to overcome the difficulty in definition of the meshing condition for the measured gear pair becomes a critical problem for this issue. Thus, the gear precision can be determined in better degree if the difficulty in definition of the meshing condition for the measured gear pair can be solved.